In conventional control processes, measurement of the current to be controlled is necessary. The current is usually measured indirectly as voltage across a measuring shunt or shunt resistor through which the current to be measured flows. The measuring current may then be deduced from the relationship of the measured voltage and the resistance of the shunt resistor through which current flows. Precise knowledge of the resistance value of the shunt resistor is of critical importance for the precision of the current measurement.
Shunt resistors are frequently used whose resistance tolerance is small enough for the current that is to be measured, and whose temperature dependency in the ideal case is zero or at least follows a known distribution. In the latter case, the voltage measured at the shunt resistor may be corrected according to the known temperature dependency. For example, the measured voltage may be corrected using a reference voltage which has the same known temperature dependency as the shunt resistor.
The reference voltage may be determined, for example, prior to initial start-up of the shunt resistor, and may be preconfigured as a reference in the measuring apparatus. However, the resistance value of metallic shunt resistors in particular may change over the course of operation, for example due to material aging. Since this material aging may be a function, among other factors, of the unknown current flow through the shunt resistor prior to initial start-up, a one-time preconfiguration of the measuring apparatus using a reference curve may not characterize the material aging.
It is known from U.S. Pat. App. Pub. No. 2011/0033985 to provide a shunt resistor whose resistance has a slight temperature dependency on an integrated circuit, it being possible to calibrate the shunt resistor using components of the integrated circuit.